1. Field of the Invention
The present invention relates to a dental syringe of the three-way type which is designed so that warm water, warm air or warm water-air mixture jet is selectively available from a nozzle without providing an electric means such as electric heater or the like in the body of the syringe.
2. Description of the Prior Art
In the prior-art three-way syringe of this type, the design is made such that compressed air is heated by means of an electric heater of a nichrome wire provided in a compressed air passage extending through the body of the syringe, a heater switch provided on the syringe body, and a transformer provided outside the syringe for reducing a power source voltage to be applied to the heater from the standpoint of safety, so that warm air blast, which is controlled to a pressure approximately equal to the atmospheric pressure, is jetted out of a nozzle portion mounted at the fore end of the syringe body, by operating a lever for compressed air and depressing the aforementioned switch; and water pre-heated outside the syringe is introduced into the syringe body through a tube provided therein so as to be jetted out of the nozzle portion. However, such a conventional arrangement is disadvantageous in that since an electric heating system is employed as means for heating compressed air as mentioned above, complex operations are involved in mounting the nichrome wire heater, heater switch and so forth; the wiring inevitably turns out complicated, which tends to cause trouble such as breaking of the heater wire, defective contact of the switch or the like; the syringe is so heavy that difficulty is experienced when it is to be handled by a dentist while being gripped by one of his or her hands; and the presence of the electric lead wires causes inconvenience in the handling of the syringe.